Habitat:  Oceanic

These animals are among the most abundant dolphins in the eastern tropical Pacific (ETP) and are the primary species involved in the tuna/dolphin interaction there. In at least the Pacific and Indian oceans, spotted dolphins associate with yellowfin tuna, spinner dolphins, and other oceanic predators; fishermen take advantage of this association to help them locate and catch tuna more efficiently.

School sizes are generally less than 100 for the coastal form, but offshore herds may number in the thousands. These gregarious animals are fast swimmers, often engaging in acrobatics, and frequently bowriding (except on the tuna fishing grounds of the ETP, where they generally have learned to avoid boats). Although pantropical spotted dolphins breed year-round, there are two calving peaks in the ETP, one in spring and one in fall.

Feeding mode:  Seizing

Broad diet characterized by:  Fish>squid>other invertebrates

Spotted dolphins feed largely on small epi- and mesopelagic fish, squid, and crustaceans that associate with the deep scattering layer. In some areas, flying fish are also important prey.

Known prey species:

Fish:  Oxyporhamphus micropterus, Exocoetus sp., Diogenichthys sp., Lampanyctus parvicauda, Myctophum aurolaternatum, Unidentified Mycotophidae, Vinciguerria sp., Bregmaceros sp., Scopelogadus bispinosus, Cubiceps carinatus, Cubiceps sp.¸ Symbolophorus sp., Myctophum aurolaternatum, Myctophum nitidulum, Myctophum asperum, Myctophum spinosum, Lampanyctus omostigma, Lampanyctus festivus, Lampanyctes idostigma, Lampadena luminosa, Diaphus splendidus, Diaphus mollis, Hygophum proximum, Hygophum reinhardtii, Diogenichthys mexicanus, Tarletonbeania crenularis, Notoscopelus resplendens, Ceratoscopelus warmingii, Taaningichthys spp., Parvilux ingens, Benthosema panamense, Cubiceps pauciradiatus, Cubiceps baxteri, Cubiceps c.f. paradoxus, Howella sp., Auxis thazard, Hyperglyphe sp., Oxyporhamphus micropterus, Bregmaceros bathymaster, Scopelarchus guentheri, Scopelosaurus c.f. harryi, Stemonosudis sp., Scopelogadus bispinosus, Vinciguerria lucetia, Ichthyococcus sp., Gonostomatidae., Xenopthalmichthys spp.

Invertebrates:  Onykia sp., Ommastrephidae, Abraliopsis affinis, Unidentified Histioteuthidae, Unidentified Chiroteuthidae, Unidentified Cranchiidae, Octopoteuthis sp., Ommastrephes bartramii, Eucleoteuthis luminosa, Sthenoteuthis oualaniensis, Dosidicus gigas, Hyaloteuthis c.f. pelagica, Nototodarus c.f. hawaiiensis, Onychoteuthis banksi, Ancistrocheirus lesuerii, Pterygioteuthis giardi, Mastigoteuthis dentata, Leachia dislocata, Megalocranchia sp., Liocranchia reinhardti, Pholidoteuthis boschmai, Thysanoteuthis rhombus, Octopoteuthis deletron, Chtenopteryx sicula, Grimalditeuthis bonplandi, Architeuthis sp., Histioteuthis dofleini, Histioteuthis meleagroteuthis, Enoploteuthis sp., Abraliopsis sp., Argonauta sp., Tremoctopus violaceus, Japatella mollis, Decapoda, Isopoda

Main threats include:

Fisheries bycatch

Harvest

Conservation status:

The IUCN classifies the pantropical spotted dolphin as “lower risk/conservation dependent”, meaning there are conservation and management programs in place that address the concerns for this species at this time. The U.S. does not list this dolphin as threatened or endangered.

The greatest known mortality of this species has been in the ETP tuna purse seine fishery for tuna. Since the interaction was first documented in the late 1960s, millions have been killed. Current mortality in this fishery has been greatly reduced by years of modifications to the fishing practices, fleet changes, and U.S. and international legislation. In addition, pantropical spotted dolphins are taken incidentally in a number of other purse seine, gillnet, and trawl fisheries throughout the range. Large direct kills occur sporadically in the Japanese small cetacean drive and harpoon fisheries, and much smaller direct kills have occurred in the dolphin fisheries of the Caribbean, Sri Lanka, Philippines, Indonesia, St. Helena, and the Laccadive and Solomon Islands.

NMFS has estimated abundance of several stocks of this species. In 1998, the Pacific population of pantropical spotted dolphins was estimated as follows coastal stock = 108,289 (CV = 0.405), northeast offshore stock = 1,011,104 (CV = 0.264), and western/southern stock = 743,166 (CV = 0.298). The Hawaiian stock was estimated to be 2,928 (CV = 0.45) in 2000. The Gulf of Mexico population was estimated in 1995 to be 31,320 (CV = 0.20). In the Atlantic, NMFS assesses population for pantropical spotted dolphins in conjunction with Atlantic spotted dolphins (S. frontalis) due to difficulties differentiating the two at sea. The best estimate of the combined species in the western North Atlantic, from the Gulf of St. Lawrence to Florida, is 13,117 (CV = 0.56).

For current information on the conservation status of this species, please consult the following websites.

International Whaling Commission

U.S. NMFS Stock Assessment Reports

Convention on Migratory Species (Appendix II, eastern tropical Pacific population and Southeast Asian population)

Genetics Genbank

Sounds Scripps Institution of Oceanography

Museum Collections Smithsonian Institution

Images Google Images

Dizon, A.E., W.F. Perrin, and P.A. Akin. 1994. Stocks of dolphins (Stenella spp. and Delphinus delphis) in the eastern tropical Pacific a phylogeographic classification. NOAA Technical Memorandum NMFS 119:20 pp.

Gerrodette, T. 1999. Preliminary estimates of 1998 abundance of four dolphin stocks in the eastern tropical Pacific. U.S. Department of Commerce, SWFSC Administrative Report LJ-99-04.

Hansen, L.J., K.D. Mullin, and C.L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of Mexico from vessel surveys. U.S. Department of Commerce, SEFSC, Contribution No. MIA-94/95-25.

Kasuya, T. 1985. Effect of exploitation on reproductive parameters of the spotted and striped dolphins off the Pacific coast of Japan. Scientific Reports of the Whales Research Institute 36:107-138.

Mobley, J.R. Jr., S.S. Spitz, K.A. Forney, R.A. Grotefendt, and P.H. Forestall. 2000. Distribution and abundance of odontocete species in Hawaiian waters preliminary results of 1993-1998 aerial surveys. U.S. Department of Commerce, SWFSC Administrative Report LJ-00-14C.

Perrin, W.F. 2001. Stenella attenuata. Mammalian Species 683:1-8.

Perrin, W.F. 2002. Pantropical spotted dolphin Stenella attenuata. Pp. 865-867 in W. F. Perrin, B. Würsig and J. G. M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.

Perrin, W.F., and A.A. Hohn. 1994. Pantropical spotted dolphin Stenella attenuata. Pp. 71-98 in S. H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Volume 5 The first book of dolphins. Academic Press.

Perrin, W.F., et al. 1987. Revision of the spotted dolphins, Stenella spp. Marine Mammal Science 3:99-170.

Robertson K.M. and S.J. Chivers. (1997) Prey occurrence in pantropical spotted dolphins, Stenella attenuata, from the eastern tropical Pacific. Fishery Bulletin 95(2) 334-348.

Waring, G.T., Quintal, J.M., Fairfield, C.P. 2002. U.S. Atlantic and Gulf of Mexico Marine Mammal Stock Assessments – 2002. U.S. Department of Commerce, NOAA technical memorandum, NMFS-NE-169.